Organosilicon compounds are used in building protection principally owing to their excellent impregnation action against water and dirt. Aqueous emulsions of organosilicon compounds are environmentally friendly and physiologically tolerated.
A problem with emulsions is that they tend to drip during overhead work. If deep impregnation of vertical surfaces of building materials is desired, the aqueous emulsions must be applied in a number of coats, since they run if applied too thickly by brushing or spraying.
Furthermore, undesired aerosols form during spray application of the emulsions. Building material surfaces which have been cleaned with water must be dried so that the emulsions can penetrate to an adequate extent.
Siloxane or silane compositions containing mineral thickeners can be applied as a thicker layer to the building materials. The siloxane or silane penetrates into the building material, leaving the thickener behind on the surface of the building material. U.S. Pat. No. 4,076,868 describes solutions of methylolysiloxane in toluene which have been thickened by means of silicon dioxide having a surface area of at least 50 m.sup.2 /g; these solutions are used for rendering building materials water repellent. These solutions are neither environmentally friendly nor physiologically tolerated.
WO 95/25706 describes the rendering of mineral building materials water repellent by means of a gelatinous composition containing silanes and/or siloxanes and a layered mineral, such as bentonite or montmorillonite.
A disadvantage of compositions containing mineral thickeners is the need for subsequent removal of the layered mineral, which must be carried out thoroughly in order to avoid discoloration of the building materials. The thickener must also be disposed of. Furthermore, the penetration depth of the silanes and siloxanes is limited, since the thickener can block the capilliaries in the building material.